A data processing system is provided with processing circuitry as well as a bank of 64-bit registers. An instruction decoder decodes arithmetic instructions and logical instruction specifying arithmetic operations and logical operations to be performed upon operands stored within the 64-bit registers. The instruction decoder is responsive to an operand size field SF within the arithmetic instructions and the logical instructions specifying whether the operands are 64-bit operands or 32-bit operands where all of the operands are 64-bit operands or all of the operands are 32-bit operands. If a switch is made to a lower exception level, then a check is made as to whether or not a register being used was previously subject to a 64-bit write to that register. If such a 64-bit write had previously taken place, then the upper 32-bits are flushed so as to avoid data leakage from the higher exception level.

The vector data path is divided into smaller vector lanes. A register such as a memory mapped control register stores a vector lane number (VLX) indicating the number of vector lanes to be powered. A decoder converts this VLX into a vector lane control word, each bit controlling the ON of OFF state of the corresponding vector lane. This number of contiguous least significant vector lanes are powered. In the preferred embodiment the stored data VLX indicates that 2.sup.VLX contiguous least significant vector lanes are to be powered. Thus the number of vector lanes powered is limited to an integral power of 2. This manner of coding produces a very compact controlling bit field while obtaining substantially all the power saving advantage of individually controlling the power of all vector lanes.

A streaming engine employed in a digital data processor specifies a fixed read only data stream defined by plural nested loops. An address generator produces addresses of data elements. A steam head register stores data elements next to be supplied to functional units for use as operands. Stream metadata is stored in response to a stream store instruction. Stored stream metadata is restored to the stream engine in response to a stream restore instruction. An interrupt changes an open stream to a frozen state discarding stored stream data. A return from interrupt changes a frozen stream to an active state.

Software instructions are executed on a processor within a computer system to configure a steaming engine with stream parameters to define a multidimensional array. The stream parameters define a size for each dimension of the multidimensional array, a null vector count (N), and a selected dimension. Data is fetched from a memory coupled to the streaming engine responsive to the stream parameters. A stream of vectors is formed for the multidimensional array responsive to the stream parameters from the data fetched from memory. N null stream vectors are inserted into the stream of vectors for the selected dimension without fetching respective null data from the memory.

A processor includes a decode unit to decode an instruction that is to indicate a source packed data that is to include a plurality of adjoining data elements, a number of data elements, and a destination. The processor also includes an execution unit coupled with the decode unit. The execution unit, in response to the instruction, is to store a result packed data in the destination. The result packed data is to have a plurality of lanes that are each to store a different non-overlapping set of the indicated number of adjoining data elements aligned with a least significant end of the respective lane. The different non-overlapping sets of the indicated number of the adjoining data elements in adjoining lanes of the result packed data are to be separated from one another by at least one most significant data element position of the less significant lane.

A processor includes a widest set of data registers that corresponds to a given logical processor. Each of the data registers of the widest set have a first width in bits. A decode unit that corresponds to the given logical processor is to decode instructions that specify the data registers of the widest set, and is to decode an atomic store to memory instruction. The atomic store to memory instruction is to indicate data that is to have a second width in bits that is wider than the first width in bits. The atomic store to memory instruction is to indicate memory address information associated with a memory location. An execution unit is coupled with the decode unit. The execution unit, in response to the atomic store to memory instruction, is to atomically store the indicated data to the memory location.

A streaming engine employed in a digital data processor specifies fixed first and second read only data streams. Corresponding stream address generator produces address of data elements of the two streams. Corresponding steam head registers stores data elements next to be supplied to functional units for use as operands. The two streams share two memory ports. A toggling preference of stream to port ensures fair allocation. The arbiters permit one stream to borrow the other's interface when the other interface is idle. Thus one stream may issue two memory requests, one from each memory port, if the other stream is idle. This spreads the bandwidth demand for each stream across both interfaces, ensuring neither interface becomes a bottleneck.

A processor core includes even and odd execution slices each having a register file. The slices are each configured to perform operations specified in a first set of instructions on data from its respective register file, and together configured to perform operations specified in a second set of instructions on data stored across both register files. During utilization, the processor receives a first instruction of the first set specifying an operation, a target register, and a source register. Next, a second instruction upon which content of the source register depends is identified as being of the second set. In response, the first instruction is dispatched to the even slice. In accordance with the operation specified in the first instruction, the even slice uses content of the source register in its register file to produce a result. Copies of the result are written to the target register in both register files.

The vector data path is divided into smaller vector lanes. A register such as a memory mapped control register stores a vector lane number (VLX) indicating the number of vector lanes to be powered. A decoder converts this VLX into a vector lane control word, each bit controlling the ON of OFF state of the corresponding vector lane. This number of contiguous least significant vector lanes are powered. In the preferred embodiment the stored data VLX indicates that 2.sup.VLX contiguous least significant vector lanes are to be powered. Thus the number of vector lanes powered is limited to an integral power of 2. This manner of coding produces a very compact controlling bit field while obtaining substantially all the power saving advantage of individually controlling the power of all vector lanes.

A streaming engine employed in a digital data processor specifies a fixed read only data stream defined by plural nested loops. An address generator produces addresses of data elements. A stream head register stores data elements next to be supplied to functional units for use as operands. Stream metadata is stored in response to a stream store instruction. Stored stream metadata is restored to the stream engine in response to a stream restore instruction. An interrupt changes an open stream to a frozen state discarding stored stream data. A return from interrupt changes a frozen stream to an active state.